Abstract

The aim of the study was to appraise
various types of phosphate fertilizers (bone meal,
superphosphate, triple superphosphate, and potassium
orthophosphate) for immobilizing metals andmetalloids
in mining-impacted soils from Broken Hill, Australia.
Soils were rich in metals (Pb, Zn, Cu, and Cd) and
metalloids (As and Sb) which were mainly contained in
minor to trace amounts of coronadite [PbMn8O16],
kintoreite [PbFe3(PO4)2(OH,H2O)6], Pb, and Zn
sulfides and sulfates (possibly sphalerite, galena,
and anglesite) as well as in unidentified soluble metalbearing
phases. Phosphate stabilization experiments
were conducted as kinetic column leaching experiments,
and chemical and mineralogical changes were assessed
using elemental, sulfur isotope, and XRD analyses as
well as electron microprobe phase mapping. The
application of phosphate fertilizer to the metalcontaminated
topsoils led to mineralogical changes,
including the formation of secondary metal-bearing
phosphates. The elemental concentrations of leachates
were used as a criterion to assess the performance of
phosphate treatments. Potassium orthophosphate fertilizer
was the most effective amendment for Cd stabilization;
superphosphate and triple superphosphate fertilizers were
the most effective amendments for Pb stabilization. By
contrast, the release of As, Cu, Mn, Sb, and Zn were not
significantly suppressed, and in several cases, increased,
using bone meal, superphosphate, triple superphosphate,
and potassium orthophosphate amendments. This study
indicates that in situ phosphate stabilization of miningimpacted
soils at Broken Hill would most likely be a
complex and impractical undertaking in residential areas
due to the risk of substantial metal, metalloid, phosphate,
and sulfate release.